NOTICES OF BOOKS. 411 
Grand Duchy of Hesse were noted, each on a separate map, and from 
the whole the most remarkable were selected as special instances ;—not 
by any means, we are informed, as a complete list of all the species 
which are natives of the Rhine valley and absent from that of the 
Weser, all those being excluded whose specific identity is open to 
doubt, as well as a considerable number which have been erroneously 
stated by authors to be natives of some parts of the Weser district, 
though well enough ascertained not to be so. 
On the question of the sufficiency of the evidence on the authority 
of which these 125 species are stated to be absent from the district of 
the Upper and Middle Weser, we caunot be expected to express an 
opinion. Their absence is in every instance stated on the authority 
of three botanists, all of them the authors of local floras, and one a 
botanist of first-rate critical accuracy. Dr. Hoffmann appears to con- 
sider that the district is so amply explored, that no doubt can be en- - 
tertained in the matter; and without pledging ourselves to the belief 
that this will hold good in all cases, we may fairly enough assume that 
in so well-botanized a country, and out of so large a number of plants as 
125, a very large proportion could not have been overlooked. We 
have therefore the very remarkable fact, that on a tract of comparatively 
speaking level country, with no alpine tracts intervening to prevent 
the migration of plants, a notable number of species have been utterly 
unable to pass over a low watershed, while they have spread through- 
out the Rhine valley in all directions, ascending the tributary streams 
on both sides, as far as the height to which the species is in the habit 
of growing. 
It must be confessed however that a survey of this list of 125 names 
shows a great part of it be composed of southern forms ; and even on a 
cursory inspection a good many of the species therein contained appear 
to have been inserted rather incautiously, and tend to a certain extent 
to neutralize the weight of evidence: we find, for example, Acer Mons- 
pessulanum, Prunus Mahaleb, Lavandula vera, Scrophularia canina, and 
Muscari botryoides, all species which are characteristic of the south of 
Europe. The list also includes Gentiana utriculosa and Geranium 
macrorhizon, doubtful natives, we fear, of any part of North Germany ; 
Ercum Ervilia and Amaranthus retroflexus, both, we presume, only na- 
turalized; the anomalous Samolus Valerandi, and such minute and local 
plants as Malazis paludosa and Elatine hexandra. These however are 
